Negative electrode for non-aqueous electrolyte secondary batteries

Abstract

A negative electrode for nonaqueous electrolyte secondary batteries including a negative electrode current collector and a negative electrode mixture layer placed on the negative electrode current collector. The negative electrode mixture layer is a layer of a mixture of a negative electrode active material, a binding agent, and a conductive agent. The binding agent includes a binding agent A made of a rubber polymeric compound and a binding agent B made of a water-soluble polymeric compound. In the case where a through-thickness cross section of the negative electrode mixture layer is halved into a current collector-side region and a surface-side region, the amount of the binding agent A in the current collector-side region is larger than the amount of the binding agent A in the surface-side region and the amount of the conductive agent in the current collector-side region is larger than the amount of the conductive agent in the surface-side region.

The invention claimed is: 
     
       1. A negative electrode for nonaqueous electrolyte secondary batteries, comprising a negative electrode current collector and a negative electrode mixture layer placed on the negative electrode current collector,
 wherein the negative electrode mixture layer is a layer of a mixture of a negative electrode active material, a binding agent, and a conductive agent; the binding agent includes a binding agent A made of a rubber polymeric compound and a binding agent B made of a water-soluble polymeric compound; and in the case where a through-thickness cross section of the negative electrode mixture layer is halved into a current collector-side region and a surface-side region, the amount of the binding agent A in the current collector-side region and the amount of the conductive agent in the current collector-side region are larger than the amount of the binding agent A in the surface-side region and the amount of the conductive agent in the surface-side region, respectively, 
 wherein the amount of the conductive agent in the current collector side region is 100% by mass of the amount of the conductive agent contained in the negative electrode mixture layer. 
 
     
     
       2. The negative electrode for nonaqueous electrolyte secondary batteries according to  claim 1 , wherein the negative electrode active material contains silicon. 
     
     
       3. The negative electrode for nonaqueous electrolyte secondary batteries according to  claim 1 , wherein the negative electrode active material contains a silicon oxide, where the atomic ratio x of oxygen to the total amount of Si is given by 0.5≤x≤1.5. 
     
     
       4. The negative electrode for nonaqueous electrolyte secondary batteries according to  claim 3 , wherein the silicon oxide is surface-coated with carbon. 
     
     
       5. The negative electrode for nonaqueous electrolyte secondary batteries according to  claim 1 , wherein an amount of silicon contained in the current collector-side region is 50% to 100% by mass of the amount of silicon contained in the negative electrode mixture layer. 
     
     
       6. The negative electrode for nonaqueous electrolyte secondary batteries according to  claim 1 , wherein the content of the conductive agent in the negative electrode mixture layer is 0.1% to 20% by mass. 
     
     
       7. The negative electrode for nonaqueous electrolyte secondary batteries according to  claim 1 , wherein the amount of the binding agent A contained in the current collector-side region is 50% to 70% of the amount of the binding agent A contained in the negative electrode mixture layer. 
     
     
       8. The negative electrode for nonaqueous electrolyte secondary batteries according to  claim 1 , wherein the negative electrode active material further contains a carbon material. 
     
     
       9. The negative electrode for nonaqueous electrolyte secondary batteries according to  claim 5 , wherein the amount of silicon contained in the current collector-side region is 100% by mass of the amount of silicon contained in the negative electrode mixture layer. 
     
     
       10. A negative electrode for nonaqueous electrolyte secondary batteries, comprising a negative electrode current collector and a negative electrode mixture layer placed on the negative electrode current collector,
 wherein the negative electrode mixture layer is a layer of a mixture of a negative electrode active material, a binding agent, and a conductive agent; the binding agent includes a binding agent A made of a rubber polymeric compound and a binding agent B made of a water-soluble polymeric compound; and in the case where a through-thickness cross section of the negative electrode mixture layer is halved into a current collector-side region and a surface-side region, the amount of the binding agent A in the current collector-side region and the amount of the conductive agent in the current collector-side region are larger than the amount of the binding agent A in the surface-side region and the amount of the conductive agent in the surface-side region, respectively, 
 wherein an amount of silicon contained in the current collector-side region is 100% by mass of the amount of silicon contained in the negative electrode mixture layer.